BOOST_CHECK_CLOSE(0, smallnumber) fails

[WilliamTambellini]

Hello
With boost 1.60
BOOST_CHECK_CLOSE(-0, -4.37113883e-08, 1)
fails with :
difference{3.40282e+38} between -0 and -4.37113883e-08 exceeds 1%
Note the difference is super big.
Should nt it pass ?
Tks

[raffienficiaud]

Hi,

There were many bug fixes since 1.60 (see here for more details).

Would you please try again with the latest version of Boost?

[raffienficiaud]

Sorry for the late investigation. It turns out that you cannot use BOOST_CHECK_CLOSE to compare to the value 0, as it would use the algorithm described here.

You have 2 options:

• either use BOOST_CHECK_SMALL(-4.37113883e-08, 1.) (note . in the 1.)
• or use BOOST_TEST(-4.37113883e-08 == 0, 1. % tt::tolerance()) (for percentage tolerance)

Hope that helps!

[WilliamTambellini]

Thank you @raffienficiaud
I have retried with 1.69 and the same behavior.
Could nt find a better perf than writing my own CHECK macro doing :
CHECK_CLOSE(result, ref)
if (result == 0 || ref == 0)
BOOST_CHECK_SMALL(result - ref, 0.01f);
else
BOOST_CHECK_CLOSE(result, ref, 0.01f);

Mathematically speaking, it is legit to wonder if 0.0000001 is "close" to 0 (within a range).
Should nt it be illogic to expect BOOST_CHECK_CLOSE() to work even if left or right are 0 ?

[raffienficiaud]

If you look at the equations for comparison here, then only equation (1) can work when one of the arguments u or v is 0. This is why there exists BOOST_CHECK_SMALL and BOOST_CHECK_CLOSE.

On the other hand, this is done automatically with BOOST_TEST if

• one of the arguments is floating point (since 1.70, otherwise the two arguments should be floating points)
• and one of the argument is zero,

so you should not be needing to write your own logic.